netdev - Re: [PATCH 1/3] net: bgmac: allocate struct bgmac just once & don't copy it

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Date:   Fri, 27 Jan 2017 11:14:50 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nbd@....name
Cc:     zajec5@...il.com, jon.mason@...adcom.com, f.fainelli@...il.com,
        nbd@...nwrt.org, netdev@...r.kernel.org, rafal@...ecki.pl
Subject: Re: [PATCH 1/3] net: bgmac: allocate struct bgmac just once &
 don't copy it

From: Felix Fietkau <nbd@....name>
Date: Fri, 27 Jan 2017 17:02:33 +0100

> On 2017-01-27 10:20, Rafa┅ Mi┅ecki wrote:
>> From: Rafa┅ Mi┅ecki <rafal@...ecki.pl>
>> 
>> To share as much code as possible in bgmac we call alloc_etherdev from
>> bgmac.c which is used by both: platform and bcma code. The easiest
>> solution was to use it for allocating whole struct bgmac but it doesn't
>> work well as we already get early-filled struct bgmac as an argument.
>> 
>> So far we were solving this by copying received struct into newly
>> allocated one. The problem is it means storing 2 allocated structs,
>> using only 1 of them and non-shared code not having access to it.
>> 
>> This patch solves it by using alloc_etherdev to allocate *pointer* for
>> the already allocated struct. The only downside of this is we have to be
>> careful when using netdev_priv.
>> 
>> Another solution was to call alloc_etherdev in platform/bcma specific
>> code but Jon advised against it due to sharing less code that way.
> How does that lead to sharing less code?
> I find this pointer indirection rather ugly and uncommon, and I think it
> would be much cleaner to split the probe into bgmac_enet_alloc and
> bgmac_enet_probe (with bgmac_enet_alloc calling alloc_etherdev and doing
> basic setup).

I agree, it would be so much better if bgmac_probe() and friends
initialized a real bgmac object which was the private of a netdev
struct, then passed that down into bgmac_enet_probe().